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Subject: Re: Terrible VM in 2.4.11+?
From: Austin Gonyou <austin@digitalroadkill.net>
To: Lukas Hejtmanek <xhejtman@mail.muni.cz>
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <20020709001137.A1745@mail.muni.cz>
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I do things like this regularly, and have been using kernels 2.4.10+ on
many types of boxen, but have yet to see this behavior. I've done this
same type of test with 16k blocks up to 10M, and not had this problem I
usually do test with regard to I/O on SCSI, but have tested on IDE,
since we use many IDE systems for developers. I found though, that using
something like LVM, and overwhelming it, causes bdflush to go crazy. I
can hit the wall you refer to then.When bdflushd is too busy...it does
in fact seem to *lock* the system, but of course..it's just bdflush
doing it's thing. If I modify the bdflush params..this causes things to
work just fine, at least, useable.



On Mon, 2002-07-08 at 17:11, Lukas Hejtmanek wrote:
> Hello,
> 
> as of the last stable version 2.4.18 VM management does not work for me
> properly. I have Athlon system with 512MB ram, 2.4.18 kernel without any
> additional patches.
> 
> I run following sequence of commands:
> 
> dd if=/dev/zero of=/tmp bs=1M count=512 &
> find / -print &
>  { wait a few seconds }
> sync
> 
> at this point find stops completely or at least almost stops.
> 
> The same if I copy from /dev/hdf to /dev/hda. XOSVIEW shows only reading or only
> writing (as bdflushd is flushing buffers). It never shows parallel reading and
> writing. /proc/sys/* has default settings. I do not know the reason why i/o
> system stops when bdflushd is flushing buffers nor reading can be done.
> 
> -- 
> Luk?? Hejtm?nek
> -
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-- 
Austin Gonyou <austin@digitalroadkill.net>
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